Flask



FIG. 1 is a bottom view of a flask showing my new design;

FIG. 2 is a side view thereof,

FIG. 3 is a front view thereof, the rear view being a mirror image thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a perspective view thereof. 

The ornamental design for a flask, as shown and described. 